Deep blue colour is imparted to glass by the presence of A. Cupric oxide B. Nickel oxide C. Cobalt oxide D. Iron oxide

The correct answer is C. Cobalt oxide.

Cobalt oxide is a blue-black powder that is used to color glass and ceramics. It is also used in pigments and in the production of cobalt-based magnets.

Cupric oxide is a red-brown powder that is used to color glass and ceramics. It is also used in pigments and in the production of copper-based alloys.

Nickel oxide is a green powder that is used to color glass and ceramics. It is also used in pigments and in the production of nickel-based alloys.

Iron oxide is a red-brown powder that is used to color glass and ceramics. It is also used in pigments and in the production of iron-based alloys.

Cobalt oxide is the only one of these oxides that imparts a deep blue color to glass. The other oxides impart different colors, as described above.